Commercial photographic printing assemblies process large volumes of negative film by sequentially creating a series of photographic prints in correspondence with a series of negative images. Generally, an enclosure houses a drive system which systematically conveys a web of photographic paper through a printer positioned within the housing. The enclosure is typically opaque to allow the exposure process to occur in a darkened environment. The drive system includes a series of spools and rollers which cooperate to direct the web of photographic paper to and from the printer. More specifically, a feed spool, adapted to retain the unexposed photographic paper in a rolled configuration, and a series of rollers cooperate to direct the unexposed paper along a feed path to the printer. After being exposed in the printer, the photographic paper is guided along a delivery path to a take-up spool which retains the exposed photographic paper in a rolled configuration for further processing.
Typically, the feed and take-up spools comprise cardboard tubes on which the photographic paper is directly wound. Initially, the photographic paper is attached to a feed spool and wound thereon. The feed spool is inserted on a spindle carried by the housing of the printer assembly and the leading edge of the photographic paper is threaded through the feed path, printer and delivery path and affixed to a take-up spool similarly mounted in the assembly. In this manner, the web is attached to both the feed spool and take-up spool prior to the printing process to ensure proper movement of the paper. In use, the drive system incrementally advances the web of photographic paper through the printer. A length of negative film is likewise advanced within the printer, and a series of photographic images are exposed on the previously unexposed photographic paper. The drive system, therefore, also operates to wind the exposed photographic paper on the take-up spool.
Several problems exist with the previously described system. First, rotation of the cardboard spools on the spindles produces dust particles inside the opaque enclosure which can contaminate the photographic negative surface and adversely affect the exposure process. Secondly, the end portions of the web of photographic paper cannot be exposed in the printer since the web is attached directly to both the feed spool and take-up spool. More specifically, a portion of the photographic paper located at the leading end of the web and generally corresponding in length to the length of the delivery path is wasted as it is initially threaded and disposed beyond the exposure stage of the printer. Likewise, a portion of the photographic paper located at the trailing end of the web and generally corresponding in length to the length of the feed path is wasted as it remains along the feed path at the end of the printing process and never reaches the exposure stage of the printer.